In order to meet the demand for wireless data traffic, which has been increasing since the commercialization of a fourth-generation (4G) communication system, efforts are being made to develop an improved fifth-generation (5G) communication system or pre-5G communication system. For this reason, a 5G communication system or pre-5G communication system is referred to as a beyond 4G network communication system or a post Long Term Evolution (LTE) system.
To achieve a high data transmission rate, implementing a 5G communication system in an extremely high frequency (mmWave) band (for example, a 60 GHz band) is considered. To relieve the path loss of signals and to increase the transmission distance of signals in an extremely high frequency band, beamforming, massive Multiple-Input And Multiple-Output (massive MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large scale antenna techniques are under discussion for a 5G communication system.
Further, to improve the network of the system, technical development in an evolved small cell, an advanced small cell, a cloud Radio Access Network (cloud RAN), an ultra-dense network, Device to Device (D2D) communication, wireless backhaul, a moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation is progressing for the 5G communication system.
In addition, an Advanced Coding Modulation (ACM) scheme including Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation (FQAM) and Sliding Window Superposition Coding (SWSC) and an advanced access technique including Filter Bank Multi Carrier (FBMC), Non Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA) are developing in the 5G system.
A Gaussian model is considered for an interference signal in order to conduct operations, such as modulation and encoding management, soft-decision decoding metric generation, and the like, with low complexity in a communication system. A Quadrature Amplitude Modulation (QAM)-based modulation scheme is generally used to render a property of an interference signal maximally close to Gaussian. However, since a non-Gaussian channel has a higher channel capacity than a Gaussian channel, a higher network throughput may be obtained in the non-Gaussian channel than in the Gaussian channel if properly reflecting the statistical properties of interference signals in system management. Accordingly, a modulation scheme for rendering an interference signal non-Gaussian is required. For this reason, Frequency and QAM (FQAM) is suggested as a modulation scheme.
FIG. 1 is a view illustrating the concept of an FQAM scheme.
As illustrated in FIG. 1, FQAM is a hybrid modulation scheme 120 in which a QAM scheme 100 and a Frequency Shift Keying (FSK) modulation scheme 110 are combined and has a property of rendering an interference signal non-Gaussian similar to FSK. Further, the FQAM scheme may substantially improve spectral efficiency (SE), as compared with the FSK scheme, by further applying the QAM scheme. FIG. 1 illustrates a 16 FQAM scheme 120 for representing 24=16 pieces of information, in which a 4 QAM scheme 100 for representing to 2 bits is combined with the FSK scheme 110 using four frequencies.
FQAM renders a property of an interference signal from a neighboring cell non-Gaussian to exhibit excellent performance in a low SINR area, as compared with QAM. However, according to the distribution of the SINRs of users scheduled by a Long Term Evolution (LTE)-based base station using a proportional fairness (PF) scheduler or the like, there is a very small proportion of users in an area where FQAM exhibits a performance gain as compared with QAM. FQAM generally has a lower SE than QAM, and FQAM shows a higher performance than QAM in an SINR area of about −3 dB or less. According to the distribution of the SINRs of users scheduled by the LTE-based base station, there are less than 1% of users in −3 dB or less, and thus there are few users at which FQAM is targeted.
That is, a very low proportion of users may experience an improved effect in spectral efficiency through FQAM.